Cooling rates, -methods

Herpfer M. A., Larimer J. W., and Goldstein J. 1. (1994) A comparison of metaUographic cooling rate methods used in meteorites. Geochim. Cosmochim. Acta 58, 1353-1365. 

Hopfe W. D. and Goldstein J. I. (2001) The metaUographic cooling rate method revised application to iron meteorites and mesosiderites. A/cteorif. Planet. Sci. 36, 135-154. 

The experimental conditions used to determine the CFPP do not exactly reflect those observed in vehicles the differences are due to the spaces in the filter mesh which are much larger in the laboratory filter, the back-pressure and the cooling rate. Also, research is continuing on procedures that are more representative of the actual behavior of diesel fuel in a vehicle and which correlate better with the temperature said to be operability , the threshold value for the Incident. In 1993, the CEN looked at two new methods, one called SFPP proposed by Exxon Chemicals (David et al., 1993), the other called AGELFI and recommended by Agip, Elf and Fina (Hamon et al., 1993). 

If exchanger shell diameter is in doubt, see Chapter 2, Heat Exchangers, the Shell Diameter section. In addition, this book provides a rough rating method for air-cooled heat exchangers. 

When film is produced by air-cooled tubular blowing methods cooling rates are slower and larger degrees of crystallinity result. Hence tubular film is slightly... 

It is clear that the nematic phase exhibits a featureless Rayleigh wing and that several distinct solid phases can be formed depending on cooling rate [79]. This includes an apparently glassy phase. The vertical tick marks indicate the calculated frequencies of vibrational modes as obtained from density functional methods. 

In addition to possible variations between methods, there may also be variations in Tg within a method, depending on the measurement protocol employed. For example, the DCS Tg midpoint for a quench-cooled ( 100 K/min) maltose sample, heated at a scanning rate of lOK/min, was 43.1 0.21 °C, whereas for a maltose sample prepared using equal heating and cooling rates of lOK/min the Tg was 41.2 0.10°C (Schmidt and Lammert, 1996). For the same samples, DSC Tg Active temperatures were also calculated. Tg Active for the quench-cooled sample was 41.0 0.20 °C, whereas for the equal-rate sample, Tg Active was 38.6 0.06 °C. 

Method Droplet Size ( im) Metal/AUoy Cooling Rate (°C/s) Throughput (kg/mm) Capacity (Metric Tons) Advantage Limitation... 

With the above-described heat transfer model and rapid solidification kinetic model, along with the related process parameters and thermophysical properties of atomization gases (Tables 2.6 and 2.7) and metals/alloys (Tables 2.8,2.9,2.10 and 2.11), the 2-D distributions of transient droplet temperatures, cooling rates, achievable undercoolings, and solid fractions in the spray can be calculated, once the initial droplet sizes, temperatures, and velocities are established by the modeling of the atomization stage, as discussed in the previous subsection. For the implementation of the heat transfer model and the rapid solidification kinetic model, finite difference methods or finite element methods may be used. To characterize the entire size distribution of droplets, some specific droplet sizes (forexample,.D0 16,Z>05, andZ)0 84) are to be considered in the calculations of the 2-D motion, cooling and solidification histories. 

Flow patterns of hydrodynamic systems like the compendial dissolution apparatus may be qualitatively characterized by means of dilute dye injection (e.g., methylene blue) or by techniques using particulate materials such as aluminum powders or polystyrene particles. Flow patterns may be also visualized by taking advantage of density or pH differences within the fluid stream. The Schlieren method, for instance, is based on refraction index measurement. Hot wire anemo-metry is an appropriate method to quantitatively characterize flow rates. The flow rate is proportional to the cooling rate of a thin hot wire presented to the stream. Using laser Doppler... 

Cooling rate (Ks ) Type of process Materials Method of reahzation... 

Polythermal methods. The temperature of an alloy sample is progressively changed, generally at a well-defined and controlled heating or cooling rate, as some properties of the sample itself are continuously measured. 

A short list of the principal experimental methods is contained in a systematic review of the subject prepared, a long time ago, by Giessen (1969), still giving valid indications about, for instance, the cooling rates achievable. 

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